Method of making pistons



7 April 24, 1934. v N WN I Y 1,956,001 Marmon OF MAKING, PISTONS,

or nal-Filed June 2, 1927 g wuemtoc B05552" N BEEN/XI.

Patented Apr. 24, 1934 @NETED STATES PATENT OFFICE METHOD OF MAKING PISTONS Robert N. Brown, Detroit, Mich, assignor to Packard Motor Car Company, Detroit, Mich,

a corporation of Michigan Application June 2, 1927, Serial No. 195,937 Renewed April 13, 1932 11 Claims. (01. 29-4565) This invention relates to internal combustion shaped hole 29 at its mid-point adapted to reengines and more particularly to means for and ceive the mandrel 13. When the pin 19 is inserted methods of grinding pistons. in the bosses it is positioned so that the center The principal object of this invention is to of the hole 29 is exactly on the axis of the piston provide a novel method of finishing pistons to and faces the bottom of the skirt. In this posi- 6O impart to the skirt during the finishing operation, tion the flanges engage the circumferential an oval or elliptical shape. grooves 26. The bolts 28 are then adjusted so The above and other objects of my invention that the conical members 27 press the expansible will become apparent from the following descripfingers 24 into intimate engagement with the wall tion taken in connection with the accompanying of the piston pin holes for rigidly retaining the pin 65 drawing, wherein: in position. The mandrel 13 includes an integral Fig. 1 shows a piston holding and grinding debi-furcated portion having legs and 31 adapted vice and a piston positioned thereon for grinding to straddle the pin 19 for applying a torque adaptin accordance with the method of this invention; ed to rotate the piston.

15 Fig. 2 is an enlarged sectional view on line 2-2 The piston 17 is shown more in detail in Figs. 70 of Fig. 1, the piston being shown rotated 90 de- 3 and 4. This piston includes a head portion 32 grees; having a ring belt provided with piston ring Fig. 3 is an enlarged elevation of the piston grooves 33, and dependent flanges or webs 37 inshown in Figs. 1 and 2, and cluding the piston pin bosses 20 and 21 and a no 7 Fig. 4 is a similar view with the piston rotated skirt portion 34 including bearing faces and 36 4 90 from the position shown in Fig. 3. formed integral with the flanges 37 and sup- The device shown in Fig. 1 includes a base 7 ported thereby. The flanges 37 have cast therein supporting driving mechanisms 8 and 9 and transverse reinforcing struts 39 adapted to prestandards 10 and 11. The mechanisms 8 and 9 vent undue expansion and contraction the ends include respectively a rotatable shaft 12 and a of the struts being imbedded in the wall of the rotatable centering shaft 13, the shaft 12 having skirt to provide suitable supports for the skirt. attached thereto a grinding element 14, the re- The piston 1'7 is preferably made of aluminum or mote end of the shaft being supported in a bearone of its alloys, but it may be made of any other ing in the standard 10. The standard 11 carries suitable material.

,, a second centering shaft 15 positioned in axial The head and S t ar pa a in p by alinement with the shaft 13, and a suitable adcircumferential slots a d 41 Cut through the justing mechanism including a control handle 16 bearing faces below the lower ring belt and exadapted to move the shaft 15 axially. The centers tending into apertures 42 adjacent to the webs 13 and 15 are adapted to support in exact axial 37. The edges of the bearing faces adjacent to alinement and to rotate piston 17 in engagement the pin bosses are tapered in an axial direction 0 O with the grinder 14. The members 13 and 15 are to provide a gradually increasing surface area, provided with points adapted to be maintained in the purpose of which will appear farther on. precise alinement parallel with the axis of rota-v The face 35 of the piston may be termed its tion of the grinder 14. The head of the piston 1'? bearing face because it is adapted to be so as- 4 is provided with a lathe center 18, Fig. 3, posisociated with the cylinder, the crankshaft and tioned accurately concentric with the piston axis, connecting rod of the engine that it will support adapted to receive the point of the pin 15. An the greater pressure during operation. The face expanding piston pin 19, Fig. 2, is inserted in the 36 which is subjected to considerably less prespiston pin holes provided in the bosses, 20 and 21. sure than the face 35, is provided with a slot 43 The piston pin 19 has recessed end portions 22 positioned at a slight angle with respect to the W3 including radial slots 23 defining flexible arcuate axis of the piston and extending from the botfingers 24 having laterally extending arcuate tom of the skirt nearly to the top thereof. Adflanges 25 arranged in a circle and adapted to enditional slots 44 and 45. extend from the bottom gage circumferential grooves 26 in the piston pin 0f the apertures 42 adjacent to the piston pin holes. Frusto-conical members 27 are positioned bosses, at an angle'of app y fi e in the respective recesses of the piston pin and with respect to the piston axis a distance about are provided with axially positioned bolts 28 half way to the bottom of the skirt. The slots threaded into the solid portion of the pin with 43, 44 and 45 allow expansion of the skirt and their heads counter-sunk in suitable recesses in prevent excessive pressure against the cylinder the members 27. The pin 19 has a radial conicalwall by enabling the skirt to yield circumferentially. The diagonal positions of these grooves also prevent scoring of the cylinder.

The ends of the piston pin bosses 20 and 21 are relieved somewhat so as not to engage the surface of the cylinder and the portions 46 of the skirt below the bosses are preferably also relieved or reduced in diameter by the method herein described, so that the cross section of the skirt at this point is substantially elliptical.

In grinding the piston, the grinding element 14, which may be an emery wheel is rotated in one direction by the driving mechanism 12, as indicated by the arrow in Fig. 2, whereas the piston 17 is rotated by the driving mechanism 13 so that its surface engaged by the grinder moves in the opposite direction, as indicated by the arrow.

The pin 19 being rigidly centered on the shaft 13 and its ends being rigidly locked in the hangers or webs 37 which are integrally connected at their adjacent ends to the narrow skirt portions 46 below the bosses, these skirt portions, which are on a diameter parallel to the axis of the pin bosses, are more firmly supported than the free bearing portions 85 and 36 at right angles thereto. The bearing portions 35 and 36 being less firmly supported than the narrow portions 46 yield inwardly so that more material is removed by the grinding wheel from the narrow portions as than from the bearing portions which are less solidly supported. Thus the skirt is ground oval or elliptical so that the lower portions 46 below the piston pin bosses are relieved and do not engage the piston cylinder upon expansion hence scoring of the cylinders and sticking of the piston is prevented.

I have also found that with the grinding wheel such as shown in my drawing the pressure per unit on the bearing faces 35 and 36 is less than on the portions 46 and as a result of this diirerence in pressure per unit area the grinder is caused to remove more material from the narrow portions 46 than from the bearing surfaces, this action also contributing toward the oval or elliptical shape of the piston.

Although this invention has been described in connection with certain specific embodiments, it is to be understood that the principles involved are susceptible of other modifications that will readily occur to persons skilled in the art, hence the invention is to be limited only as indicated by the scope of the appended claims.

What is claimed is:

1. The method of producing a piston com risthe skirt of the piston with hearing aving their edges tapering in an axial ection, slotting at least one of the bearing and rotating the piston in engagement with a grinding element.

2. The method of producing a piston comprising forming the skirt of the piston with bearing faces having their edges tapering in an axial direction, adjacent portions of the skirt and the head, slotting the skirt in substantially an axial direction and rotating the piston in engagement with a grinding element.

3. The method of producing a piston comprising forming the skirt of the piston with openings on each side of the piston pin bosses and with bearing faces having their edges tapering in substantially an axial direction, slotting the skirt in an axial direction and rotating the piston in engagement with a grinding element having a width equal to the length of the piston.

4. The method of producing a piston comprising forming the skirt of the piston with similar bearing faces having their edges tapering in substantially an axial direction, slotting one of the bearing faces and rotating the piston in engagement with a grinding element extending the entire length of the piston.

5. The method of producing a piston comprising forming a piston with openings adjacent the piston pin bosses and with skirt portions having their edges tapering in an axial direction and supported by the piston pin bosses, slotting at least one of the skirt portions intermediate the bosses and rotating the piston in engagement with a grinding element extending the entire length of the piston.

6. A method of producing a piston comprising forming the skirt with relieved surface areas at the end of the pin. bosses and tapering the surface area adjacent the sides of the relieved areas in an axial direction, and rotating the piston in fixed engaging relation with a grinding wheel.

'7. The method of finishing a hollow, cylindrical article which comprises supporting the interior in such a way as to hold. an open end portion of the wall more firmly along one diameter of the article than along a second diameter at right angles to the first diameter, and then grinding the exterior of the article.

8. The method of finishing a hollow, cylindrical article having a closed end, which comprises holding a true center on the closed end, supporting the interior in such a way as to hold the open end portion of the wall of the article more firmly along one diameter than along a second diameter at right angles to the first diameter, and then grinding the exterior of the article.

9. The method of finishing a piston having a closed head and pin bosses, which comprises holding a true center on the closed end, supporting the interior in such a way as to support the open end wall of the piston more firmly along a diameter parallel to the axis of the pin bosses than along a diameter at right angles to the axis of the pin bosses, and then grinding the exterior of the article.

10. The method of finishing a hollow, cylindrical article, which comprises supporting the interior in such a way as to support the wall of the article at an open end portion more firmly along grinding wheel and the piston, the pressure reone diameter than along a second diameter at an lation of the wheel with the piston finishing the skirt in elliptical cross-section.

ROBERT N. BROWN. 

